Recently, demands on high-resolution and high-quality images such as High Definition (HD) images and Ultra High Definition (UHD) images are increased in various fields. As image data include more high-resolution and high-quality images, compared to typical image data, the amount of information and the amount of bits for transmission are relatively increased. Therefore, when image data are stored using a medium such as an existing wired/wireless broadband line or image data are stored using an existing storage medium, transmission costs and storage costs are increased. In order to resolve such limitations, high-efficiency image compression techniques may be used.
The Image compression techniques include an inter prediction technique for predicting pixel values in a current picture from the previous and/or following pictures of the current picture, an intra prediction for predicting pixel values in a current picture by using pixel information in the current picture, and an entropy encoding technique for allocating a short codeword to a high frequency value and a long codeword to a low frequency value. By using such image compression techniques, image data may be effectively compressed for transmission or storage.